Method for high pressure condensate return



Nov. 6, 1934. .1. B. STICKLE METHOD FOR HIGH PRESSURE CONDENSATE RETURN Filed OCh. 24, 1931 W r h ATTORNEYS.

35 boiler.

Patented Nov. 6, 1934;

1 time 1:

isiatsn METHOD ron HIGH PRESSURE CQNIDENSATE RETURN;

Jchn B. Stickle, Indianapolis, Ind. 7 Application October 24, 1931, Serial No. 570,806

4 Claims.

The object of this invention is to effect an appreciable saving in the operation of a high pressure condensate return system, used for any purpose, by a material saving in the heat of the con- "densate which is returned to the boiler and, therefore, the fuel required to operate the latter.

The operation of many processes by steam heat requires steam temperatures corresponding to steam pressures considerably higher than atmospheric pressure. In such processes steam must be supplied to processing units at these higher pressures and the condensate must be removed at or near the same high pressures. The condensate removal has heretofore been accomplished by the use of steam traps or the like which receive the an example where a process requires a steam temperature of 353 F. the steam must be supplied to the process unit at or above the corresponding steam pressure of 125 pounds per square inch gauge and the condensate is delivered to the steam traps at the temperature of 353 F. The condensate in the atmospheric reservoir however falls to the temperature corresponding to atmospheric pressureor 212 F. The heat of the condensate represented by the diiierence between 353 and 306 212 or 141 B. t. u. of heat per pound of condensate is absorbed in the formation of steam in the condensate reservoir. This so-called flash steam escapes through the vent and the heat therein is lost and can not be returned to the The object of the present invention is to conserve and return tothe boiler a large proportion of the great amount of heat that has hitherto been lost in this manner and to make a corresponding reduction in the amount and cost of fuel required to operate the boiler.

The chief feature of the invention consists in providing an automatic control of the vent from the condensate tank by means of which the pressure in the condensate tank is maintained above atmospheric pressure but not sufiiciently high to prevent proper drainage of the system. In this manner the condensate in the tank is maintained at a much higher temperature than 212 F. and because of its high pressure it may be pumped into -the boiler at this higher temperature without 3 gauge pressure, I prefer for many installations to maintain the condensate in the reservoir under" approximately 100 pounds per square inch gauge pressure, corresponding to 338 F. temperature, thus providing 25 pounds per square inch pressure drop for adequate drainage of the processing system and steam traps. The condensate is therefore returnedto the boiler at or near 338 F. and there is thus a heat saving of 126 B. t; u. per pound of condensate returned over the systemin which the condensate is returned at or near 212 F.

In addition to'th'e primary saving in heat dis cussed above, my inventionm'akes a'saving in the amount of make-up water and thus makes i a secondary heat saving as well as saving the cost a of the additional water. Continuing the previously assumed example, when condensate at 353 F. is discharged into a reservoir at atmos-- pheric pressure 14.8% or approximately one' seventh flashes into steam and is lost through the vent. Make-up watenusually at about F; must be supplied to the boiler to replace this loss. l When the same condensate at 353 F. is discharged into my'reservoir maintained at 100 pounds per square inch gauge pressure only 1.7%

flashes into steam and is lost through my auto-' matically controlled vent. Thus, in theold sys tem approximately one-seventh of the water evaporated by the boiler is supplied thereto at 70 F. while by my invention only about 2% reaches the boiler at this low temperature, the

tional saving in the steam or electric power re--' quired for operating the condensate return pump. In the prior-systems the pump receives the condensate at atmospheric pressure and must work against a pressure head of 125 pounds per square inch to force the water into the boiler mentioned in the example. In my invention the pump receives the water at pounds per square'inch pressure and so operates against a pressure head of only 25 pounds per square inch. The pump therefore requires only one-fifth as much steam 100 or electricity for its operation.

The total heat saving resulting from the foregoing saving factors in the assumed example amounts to approximately 15% of the total heat supplied by the boiler and therefore results in a saving of the same percentage in the amount and cost of fuel, in addition to the saving of nearly the entire make-up water cost. In other examples the saving will be more or less than the just quoted, depending upon Whether the steam pressures used are higher or lower and upon whether the pressure difference required for drainage of a particular system is less or greater than that assumed.

As described herein, the automatic control of the vent consists of a vent valve which is controlled by the pressure from the boiler or supply line counteracted by the pressure from the condensate tank or return: line, and an adjustable weighted lever, or the like, cooperating with the latter, whereby only sufficient steam is allowed to escape from the tank to prevent the pressure therein from becoming to high for positive drainage and whereby the heat of the condensate is retained in the water that is returned to the boiler. If the-boiler or supply line pressure drops, the vent valve opens enough to automatically lower the return line pressure so as to maintain the desired pressure drop between the supply line and return line for good drainage;

The fullnatureof the invention will be understood from the accompanying drawing and the following: description and claims:

In the drawing, Fig. 1 is a diagram ofa portion of a high pressure return. system including my invention Fig. 2 is a vertical cross section on-the line 2-2 of Fig. 1, through the means for controlling the air vent from. the condensation tank.

In the drawing, there isshown a commonfor of. a steam supply andcondensate return system,

including a boiler 10 with a. steam line 11=1eading therefrom. From said steam line 11, there is abranch line 12 running to a: high pressure steam process unit consisting; of a chamber 112' and a pair of steam traps 13 and 14 connected therewith bypipes 15 and 16.

From the high pressure steam process unit, steam passes through pipes 17. and 1-8 to a return line 20 that, goes to acondensate tank or receiver 21 in which condensatecollects. 25 takes the water or. condensate from said tank 21- through pipe 23 and pumps it back. 45 through pipe 24 to the boiler.

In said lines so far described, there arethe usual cut-01f valves .30, 31, 32.33, 34 and 35.,

The pump is operated by steam througha supply" line 40 extending from the mainsteam. line 11 and running to the pump. In said line, there;

are; cut-oft valves 4L and 42-, Between. said valve 42 and the pump, there is a valve 43 whichzis' controlled by the level of thev condensate 111E the tank 21 through; the instrumentality-of the levers 44 and 45- and anintervening connecting; rod 46. Lever 45. is fulcrumed at 4'7 and. extends into the condensate tank 21 and has on its-inner end a float 48 which rides on the condensate 49 tank.

The foregoing system or means may, so far as this invention is concerned, be deemed to be old, and in such old system, there is an air vent or pipe 50, leading from the topof the condensation tank 21 to the atmosphere.

The" new system and invention consists in controlling said passage 50- from the condensation tank 21 to' the atmosphere. As herein illustrated, this is accomplished by means: of a differential vent valve which inturnis controlled by the differential in pressure between the boiler pressure or supply line pressure and the pressure in the. condensate tank with an adjustable weight or spring cooperating with the foregoing for the adjustment and control ofsaid vent valve. A diaphragm 61 is secured in the diaphragm casing in said the return line.

62 and connected with valve 60 by connecting rod 63. The boiler pressure or supply line pressure is xerted against the underside of diaphragm 61 through pipes 40 and 64. The pressure from the condensation tank 21 acts on the upper side of said diaphragm through pipe 65. Pipes 64 and 65 have in them cut-ofi valves 66 and 6'7. A weight 68, slidably mounted on a graduated lever 69, cooperates with the pressure from the condensate tank 21 to open the valve 60 against the pressure from the steam boiler. The lever 69 is fulcrumed between its ends at 70 to the valve stem 63 and said lever is pivoted near its end at '71 to a frame '12 which is secured to the diaphragm casing 62 and to the casing of the valve 60.

In the operation of this system the pressure of the steam supply line 11 is exerted upon the underside of the diaphragm 61 while the pressure of the return line 20 and the tank 21 is exerted upon the upperside of saiddiaphragm. The weight 68 is adjusted on the lever arm 69- so that the said weight exerts suflicient pressureupon. the upperside of the diaphragm 61 toover- I sure forces the diaphragm 61 upwardly to-close:

the valve and to prevent thereby the escape of.

flash steam from the tank 21. The further va-- porization of flash steam in the tank 21 then.

raises the pressure therein until the desired pressure difference between the supply line and return line is restored. Conversely, a decreasev in the supply line pressure or an increase in the return line pressure causes a downward. movement of the diaphragm 61 which opens the valve and permits the escape of sufiicient flash. steam from the tank 21 to restore the desired pressure difference.

The diiferential vent valve mechanism is auto.- matic and maintains a set pressure drop for positive drainage under all conditions. If the boiler pressure or supply line pressure drops, the vent valve opens automatically and thus lowers. the return pressure to maintain the required dropfor positive drainage of the process unit. Con-- versely, if the boiler pressure or supply line pressure increases, the vent valve is moved to. de-- crease-the amount of escaping steam. and to raise the pressure "m the tank to a maximum consistent with proper drainage.

The system can be advantageously applied to .take the condensation from paper machines and.

textile drying machines and other machines wherein the drying temperature is varied during the process. In these cases, the differential vent valve on the tank has the high pressure side of the diaphragm connected to the supply line and the other side of the diaphragm connected to The weight is adjusted to give the difference in pressure or drop in pressure required to make positive drainage. As the steam pressure is raised to raise the drying temperature, the condensation tank pressure is raised automatically and the condensate is pumped into the boiler at a higher pressure and temperature. If any conditions require a lower temperature steam, the pressure is lowered. This will automatically open the vent valve on the tank and lower the return line pressure to maintain the required drop in pressure for good drainage.

Another advantage of the system is that it permits the use of steam traps operating on a relatively low pressure difierence. The use of steam traps operating between 150 pounds pressure and atmospheric pressure requires a much more expensive and complicated type of trap than can be used with a pressure difference of 25 pounds and trap failures are much more frequent in the former case than in the latter,

While the foregoing specification describes a preferred form of the invention, the details thereof may be varied without departing from the scope of the invention as defined by the appended claims. For example, I do not wish to limit myself to a reciprocating steam pump for condensate return. The pump used may be a centrifugal pump electrically driven, an injector or other type of pumping apparatus, such as the so-called return steam traps.

The invention claimed is:

1. A method of returning condensate to a boiler from a high pressure heat exchange unit in which steam supplied. by said boiler is condensed, said method including the steps of discharging said condensate from said heat exchange unit into a condensate return system maintained above atmospheric pressure but at a lower pressure than that in said unit, collecting a suflicient body of condensate in said system to maintain the temperature thereof at a point permitting a portion of said condensate to flash into steam, permitting the escape of flash steam from said return system to the atmosphere to maintain the pressure in said return system sufficiently below the pressure in said unit for adequate drainage of said unit but limiting the said escape of flash steam to maintain said return system pressure above atmospheric pressure under normal load conditions for preventing unnecessary reduction in the temperature of the condensate therein, and returning the condensate from said return system to the boiler without substantial further reduction of the pressure thereof.

2. A method of returning condensate to a boiler from a high pressure heat exchange unit in which steam supplied by said boiler is condensed, said method including the steps of discharging said condensate from said heat exchange unit into a condensate return system maintained above atmospheric pressure but at a lower pressure than that in said unit, collecting a sufficient body of condensate in said system to maintain the temperature thereof at a point permitting a portion of said condensate to flash into steam, permitting the escape of flash steam from said return system to the atmosphere in such amount as to maintain a predetermined pressure difference between the pressure in said unit and said return system and to maintain said return system above atmospheric pressure for preventing unnecessary reduction in the temperature of the condensate therein, and returning the condensate from said return system to the boiler without substantial further reduction of the pressure thereof.

3. A method of returning condensate to a boiler from a high pressure heat exchange unit in which steam supplied by said boiler is condensed, said method including the steps of collecting condensate from said heat exchange unit in a condensate reservoir maintained above atmospheric pressure but at a lower pressure than that in said unit, collecting a suflicient body of condensate in said system to maintain a temperature permitting a portion of said condensate to flash into steam, permitting the escape of flash steam from said reservoir in such amount as to maintain a predetermined pressure difference between the pressure in said unit and in said reservoir and to maintain said reservoir above atmospheric pressure under normal load conditions, and pumping condensate from said reservoir to said boiler whenever a predetermined volume thereof has accumulated in said reservoir.

4. In a high pressure heating system including a boiler, a high pressure heat exchange unit and a system for returning condensate from the heat exchange unit to the boiler, the method of returning the condensate from the heat exchange unit to the boiler which includes the steps of discharging said condensate from said heat exchange unit into said condensate return system, maintaining said condensate return system above atmospheric pressure but at a lower pressure than that in said unit and at a temperature such that a portion of said condensate will be flashed into steam, collecting said condensate in the presence of a substantial body of said flash steam, permitting the escape of flash steam from said body to the atmosphere in amount such as to maintain the pressure in said return system sufiiciently below the pressure in said unit for adequate drainage of said unit but limiting said escape of flash steam to maintain said return system pressure above atmospheric pressure under normal load conditions for preventing unnecessary reduction in the temperature of the condensate therein, returning the condensate from said return system to the boiler without substantial further reduction of the pressure thereof and controlling the escape of flash steam to the amount stated by the difference in pressure existing in said boiler and condensate return system.

JOHN B. STICKLE. 

